I. Field of the Invention
Embodiments of this invention are directed generally to biology, medicine, and immunology. Certain aspects are directed to glycoprotein-immunoglobulin fusion proteins.
II. Background
Stable transgenic plants have been used to produce a variety of non-plant proteins. One use of stable transgenic plants is the production of virus-like particles (VLPs) for use in vaccines. VLP-forming antigens of different origins expressed in transgenic plants have been shown to assemble into VLPs, and their immunogenicity have been demonstrated in experimental animals when delivered by injection of purified forms or by oral consumption of unprocessed plant tissues (reviewed in Santi et al., 2006; Thanavala et al., 2006). Phase I clinical trials using transgenic plant-derived hepatitis B surface antigen (HBsAg) and Norwalk virus capsid protein (NVCP) VLPs showed safety and oral immunogenicity in humans (Tacket et al., 2000; Thanavala et al., 2005). However, long generation time and modest levels of antigen accumulation (<1% total soluble protein or <0.1 mg/g fresh weight) are two main factors limiting the practical application of transgenic plants for commercial production of VLPs.
Plant virus-based transient expression has the potential of achieving high-level antigen accumulation in a short period of time (≤2 weeks) (reviewed in Canizares et al., 2005; Gleba et al., 2007; Lico et al., 2008; Yusibov et al., 2006). However, the difficulty in genetic manipulation of large full-length or near-full-length viral genomes and inconvenient infection procedures, which some times involve in vitro transcription of DNA to infectious RNA and the co-delivery of multiple DNA/RNA segments, represent major challenges in commercial application of this technology. For example, even the new generation tobacco mosaic virus (TMV)-based “deconstructed” vector system, requires simultaneous cointroduction of three vector modules into same cells for in planta assembly of the RNA replicon (Marillonnet et al., 2004). Thus, further development of simple, easily manipulated viral vectors (e.g., vectors to produce vaccine antigens and the like) is warranted. Such technology, and the products of using such technology, would provide additional compositions and methods for producing and using glycoprotein antigens for therapy and vaccination.
The need for further development of these technologies is exemplified by the need for additional compositions and methods for treating Hepatitis C virus (HCV) infections. More than 170 million people worldwide are chronic carriers of HCV (Delwaide et al. 2000). There is neither a prophylactic nor a therapeutic vaccine currently available for HCV. The route of infection is via blood and other body fluids and over 70% of patients become chronic carriers of the virus. Persistent infection results in chronic active hepatitis which may lead to progressive liver disease (Alter et al., 1999). Presently, the only therapy for hepatitis C infection is interferon-α (IFN-α) and Ribavirin. However, this therapy is expensive, has substantial side effects, and is effective in only approximately 50% of a selected group of patients. Therapeutic vaccines that enhance host immune responses to eliminate chronic HCV infection will be a major advancement in the treatment of this disease.
The immune system plays a key role in the outcome of an HCV infection. Most individuals that are exposed to HCV mount a broad strong and multi-antigen-specific CD4+ (regulatory) and CD8+ (cytotoxic) T cell response to the virus. These individuals develop only a self-limited infection. However, in some individuals exposed to HCV, a weak or undetectable and narrowly focused immune response results in chronic infection.
There is a need for additional therapies for infections such as HCV. Therapies can include vaccines that target heteromeric glycoproteins from a variety of animals, plants and microbes; particularly those therapies that enhance or induce immune responses to viruses that produce heterodimeric envelope proteins.